Fabio Panzieri's research while affiliated with University of Bologna and other places

In the aftermath of a natural calamity, relief operations can be hindered by damages to the terrestrial infrastructures (e.g. cellular base stations) that might lead to the disruption of wireless communication services. As a result, network partitions made up of isolated End-User (EU) devices, heterogeneous in terms of wireless access technologies and transmitting frequency bands, can occur within the scenario. In this paper, we address the problem of how to deploy a temporary and dynamic wireless network in order to quickly re-establish the end-to-end connectivity among isolated devices in a post-disaster environment. To this purpose, we propose the utilization of Repairing Units (RUs), consisting of Unmanned Ground Vehicles (UGVs) equipped with multiple Cognitive Radio (CR) devices; swarms of RUs are able to self-organize into a Repairing Mesh Network (RMN) that connects the isolated EU devices. Three main contributions are provided in this paper. First, we address the theoretical problem of determining the optimal deployment of the RMN (in terms of position and channel allocation on each RU), so that the number of connected EU devices is maximized, given a constrained number of available RUs. We further divide the deployment problem into a multi-channel spatial coverage and mesh connectivity problems, and we provide an approximated (optimal) solution. Second, we propose a distributed algorithm—based on the virtual spring force model—through which the RUs are able to explore the scenario in terms of space/frequency, and to create the RMN. Third, we evaluate connectivity and adaptiveness of the distributed solution through extensive Omnet++ simulations and a small scale test-bed. Simulation results show that the distributed RMN deployment algorithm provides performance close to the approximated solution in terms of covered EU devices. Experimental results demonstrate the ability of the distributed virtual spring model to adapt to dynamic propagation conditions, in order to maximize the quality of the wireless links of the RMN.

This work presents a comprehensive and structured taxonomy of available techniques for managing the handover process in mobility architectures. Representative works from the existing literature have been divided into appropriate categories, based on their ability to support horizontal handovers, vertical handovers and multihoming. We describe approaches designed to work on the current Internet (i.e. IPv4-based networks), as well as those that have been devised for the "future" Internet (e.g. IPv6-based networks and extensions). Quantitative measures and qualitative indicators are also presented and used to evaluate and compare the examined approaches. This critical review provides some valuable guidelines and suggestions for designing and developing mobility architectures, including some practical expedients (e.g. those required in the current Internet environment), aimed to cope with the presence of NAT/firewalls and to provide support to legacy systems and several communication protocols working at the application layer.

Spontaneous wireless networks constructed out of mobile end-user devices (e.g. smartphones or tablets) are currently receiving considerable interest as they enable a wide range of novel, highly pervasive and user-centric network services and applications. In this paper, we focus on emergency-related scenarios, and we investigate the potential of spontaneous networks for providing Internet connectivity over the emergency area through the sharing of resources owned by the end-user devices. Novel and extremely flexible network deployment strategies are required in order to cope with the user mobility, the limited communication capabilities of wireless devices, and the intrinsic dynamics of traffic loads and QoS requirements. To this purpose, we propose here a novel approach toward the deployment of spontaneous networks composed by a new generation of wireless devices – called Stem Nodes (SNs) – to emphasize their ability to cover multiple network roles (e.g. gateway, router). The self-organization of the spontaneous network is then achieved through the local reconfiguration of each SN. Two complementary research contributions are provided. First, we describe the software architecture of a SN (which can be implemented on top of existing end-user devices), and we detail how a SN can manage its role set, eventually extending it through cooperation with other SNs. Second, we propose distributed algorithms, based on swarm intelligence principles, through which each SN can autonomously select its role, and self-elect to gateway or router, so that end-to-end performance are maximized while the lifetime of the spontaneous emergency network is prolonged. The ability of the proposed algorithm to guarantee adaptive and self-organizing network behaviors is demonstrated through extensive Omnet++ simulations, and through a prototype implementation of the SN architecture on a real testbed.

Spontaneous networks among end-user devices (e.g. smartphones, tablets) can guarantee emergency communication in post-disaster scenarios where the original infrastructure has been partially damaged by the occurrence of casualties. However, the heterogeneity of devices and wireless access technologies pose important challenges on the network deployment and management. In this paper, we propose the STEM-Net architecture as a viable network model to handle the heterogeneity and to enable spontaneous networking functionalities in post-disaster scenarios. In STEM-Net, the wireless devices -called Stem Nodes (SN)- are able to adapt their transmitting configurations, cover different roles (e.g. router, bridge, etc) according to the system needs and evolve their functionalities through cooperation with other nodes. Here, we provide a proof-of-concepts of the principles of nodes' mutation and evolution, by discussing how heterogeneous enduser devices provided with SN capabilities can dynamically selforganize into multi-hop networks, and share the Internet access by switching among three roles: stub, transit and gateway SNs. A bio-inspired gateway selection mode is proposed to allow each SN device to select the current role, based on the system needs and on the individual hardware characteristics and resources (e.g. residual energy or queue occupation). The simulation analysis conducted with the Omnet++ tool demonstrates the effectiveness of the STEM-Net framework in prolonging the network lifetime while providing adequate bandwidth for emergency communication to the end-users devices.

In this paper, we address the problem of reestablishing the network connectivity in post-disaster scenarios, where the original wireless infrastructure has been partitioned into multiple network fragments (called islands), operating on different frequencies. To this purpose, we propose the utilization of swarms of dedicated repairing units, called Stem-Nodes (SNs). SNs are provided with Cognitive Radio (CR) and self-positioning capabilities, in order to offer maximum reconfigurability in terms of mobility and wireless technologies supported. Moreover, swarms of SNs can self-organize into STEM-Mesh structure, that works as a dynamic backbone to connect heterogeneous islands using different technologies (e.g. Wi-Fi, Wi-MAX, etc). In this paper, we present three contributions pertaining to STEM-Mesh: (i) we describe a distributed motion control scheme (based on virtual springs approach) that enables SNs to self-organize into dynamic STEM-Mesh structures, (ii) we introduce a discovery scheme, through which SNs can explore the scenario in both spatial and frequency domains, and possibly connect the islands to the STEM-Mesh backbone and (iii) we validate the correctness of the proposed scheme, by verifying the optimal placements of the SNs composing the STEM-Mesh on a simplified scenario (e.g. chain topology). Finally, we evaluate through Omnet++ simulations the ability of STEM-Mesh to maximally re-establish connectivity on partitioned network scenarios.

The heterogeneity of current telecommunication access technologies is dramatically increasing the complexity and costs required for the set-up and maintenance of the network by service providers, and it is also posing important limitations in terms of network interoperability from the end-users' perspectives. For these reasons, research on wireless systems has investigated the possibility to deploy wireless devices with self-organizing and self-managing capabilities. However, most of these approaches limit the re-configuration capabilities to a specific layer (e.g. routing), and do not investigate the property of reconfiguration of the network as a whole. In this paper, we propose an alternative architecture (called STEM-Net) for network infrastructure deployment, extension, and management. In STEM-Net self-organization is managed through fully-reconfigurable wireless devices (called stem-nodes), that can undergo mutations to fulfill a specific tasks, like their biological counterpart. In this work we present the main characteristics of stem-nodes, and we discuss how their evolutionary behaviour can result in an extreme flexibility of the whole network segment, transforming the technological heterogeneity from a limitation to a richness.

Always Best Packet Switching (ABPS) is a novel approach for wireless communications that enables mobile nodes, equipped with multiple network interface cards (NICs), to dynamically determine the most appropriate NIC to use. Using ABPS, a mobile node can seamlessly switch to a different NIC in order to get better performance, without causing communication interruptions at the application level. To make this possible, NICs are kept always active and a software monitor constantly probes the channels for available access points. While this ensures maximum connection availability, considerable energy may be wasted when no access points are available for a given NIC. In this paper we address this issue by investigating the use of an "oracle" able to provide information on network availability. This allows to dynamically switch on/off NICs based on reported availability, thus reducing the power consumption. We present a Markov model which allows us to estimate the impact of the oracle on the ABPS mechanism: results show that significant reduction in energy consumption can be achieved with minimal impact on connection availability. We conclude by describing a prototype implementation of the oracle based on Web services and geolocalization.

This paper introduces a theoretical model of the Always Best Packet Switching (ABPS) communication mechanism, a novel mechanism for wireless communications we have developed in order to enable mobile nodes, equipped with multiple network interface cards (NICs), to determine dynamically the most appropriate NIC to use as single point of access to the Internet. Using ABPS, a mobile node can seamlessly switch to another NIC, based on the performance of the NIC currently in use, in order to get better performance. ABPS supports dynamic NIC switching without causing communication interruptions at the application level. We use Markov reward models to efficiently estimate the availability and power consumption of ABPS, SIP-based mechanisms and conventional connection-oriented protocols employing a single NIC.

In this work we investigate the performance of the Always Best Packet Switching (ABPS) operation approach. ABPS is a cross-layer wireless communication scheme that enables mobile terminals to exploit its multiple Network Interface Cards (NICs) concurrently. The ABPS software module installed on the mobile terminal determines dynamically the most appropriate NIC to use as single point of access to the Internet, and can switch to another NIC dynamically and transparently to the applications. For the assessment, we propose a performance model based on Markov reward models. Through it, we estimate the availability, reliability and throughput provided by ABPS, a standard SIP-based approach and conventional communication protocol employing a single NIC. Results show the performance improvements introduced by ABPS.

The lack of reliable communication is still an obstacle for enhanced mobile health services. The new m-Hippocrates software architecture aims to significantly improve mobile health applications using an application-level communication technology called Always Best Packet Switching.